How about STEVAL-SMARTAG1 No power mode?

[Schuyler]

Currently purchased with the STEVAL-SMARTAG1, it was discovered that the capability collected through the ST25 powers the L0 via EH pin VDD while collecting data from the sensor. I need to collect signals by thermocouple, which is the same transmission mode as SPI. Can I successfully collect data in this way? Any better suggestions?

[Michael GALIZZI]

Hello,

the EH pin provides a very limited current and a very unstable voltage. Therefore, an LDO is used to stabilize the voltage to the MCU to 1.8 V. The thermocouple (such as the MAX6675) requires higher operating voltage (3.0 V to 5.5 V) and an higher current than that the ST25 is able to provide.

Best regards,

Michael

[Schuyler]

Hi, @Michael GALIZZI 

Yes, where VDD can wake up the mcu, but can not meet the MAX6675 requirements, then L0 has other 3.3v voltage? Can I design a voltage pin with a 3.3v output from the VDD voltage?

[John TRAN]

Hi there, The Smartag1 voltage rail is 1.8V in energy harvesting mode ( no battery). so there is no option for delivering 3.3V. 

Normally with a phone, the ST25DV will not deliver more than 3V @2mA.